Hello, the problem is probably caused by liquid entering the tablet. iFixit has some excellent guides and wikis for this specific issue that should provide a good starting point for your repair. I’ll share the links below, but here’s a quick rundown: you’ll need to open the device and clean off any corrosion from the internal boards. Depending on the extent of the liquid damage, you might also need to replace the battery.

I know that this answer is a few years late, but hopefully it will help anyone else experiencing a similar issue.

• Electronics Water Damage Wiki
• Laptop is Liquid Damaged Wiki
• iPhone Liquid Damaged Repair Guide